Fastener driving apparatus



June 22, 1965 DOYLE I 3,190,187

FASTENER DRIVING APPARATUS Filed Dec. 21, 1962 3 Sheets-Sheet 1 INVENTOR.

Flak/A20 H. Dov/.5 BY

Ar TOEA/E Y5 June 22, 1965 DOYLE 3,190,187

FASTENER DRIVING APPARATUS Filed Dec. 21. 19,62 3 Sheets-Sheet 2 all INVENTOR. I R/c/lAeo H Done Afro/mars.

June22, 1965 V R. H. DO Y| E 3,190,187v

FASTENER DRIVING APPARATUS Filed Dec. 21, 1962 32 3 Sheets-Sheet 3 I06 w y J /32 INVN TOR. k/Cfi/AED H. 00 m5 ATTORNEY United States Patent 3,199,187 FASTENER DRIVING APPARATUS Richard H. Doyle, Mount Prospect, 11]., assignor to Fastener Corporation, Franklin Park, ill., a corporation of Illinois Filed Dec. 21, 1962, Ser. No. 246,608

18 Claims. (Cl. 91403) This invention. relatesto a fastener driving tool and,

more particularly, to a fastener driving tool including new and improved pneumatic piston return means. I

The use of a compression spring to return the piston in a pneumatic fastener driving tool to its normal at the end of a power stroke has largely been supplanted by pneumatic piston return means. These piston pneumatic return systems, which can avoid the failures of prior tools due to the fatigue of the return spring and also permit a reduction in the height or size of the tool, commonly use such techniques as continuously supply the pressure fluid to a differential piston or selectively applying compressed air below the piston following the termination of the power stroke. Some of these types of return systems suffer from the disadvantage that theyreduce the drive power of the too1,,an'd others of the system consume an excessive amount of the pressurizedfluid or require somewhat complicated valve arrangements for controlling the flow of the piston return fluid.

Accordingly, one object of the present invention is to Another. object is to provide a pneumatic piston return systemrincluding means for selectively supplying a pressurized fluid that returns a piston in dependence on the pressure within the cylinder.

Another objectis to provide a pneumatic return system in which a valve is pneumatically operated in dependence on the position of. the drive piston to control the flowof a pressurized fluid to the cylinder. 7

Another object is to provide a fastener driving tool of the type including a movable cylinder in which a fluid operated valve carried on the cylinder controls the application of a pressurized fluidto the cylinder for returning the piston. r

A further object is to provide a fastener driving tool in 'which the.connection of the interior of one end of the cylinder to the atmosphere at the end of adrive stroke of a piston controls a pistonreturn means to supply pres: surized fluid to another portion of the cylinder to return the piston.

A further object is to provide a fastener driving tool including new and improved means for selectively discharging fluid from the interior of the cylinder.

Another object is to provide afastener driving tool including both a cylinder movable into and out of engagement with a fixed position main valve means and a piston actuated valve for selectively connecting the interior of the cylinder to the atmosphere.

r In accordance with these and many other objects, an

embodiment of the invention comprises a fastener driving tool having a housing defining-a reservoir continuously supplied with compressed air in which is slidably mounted a cylinder. A main valve means carried on the housing immediately above an openend of the cylinder is selectively engaged by moving the cylinder relative to the ice inder is selectively placed in communication with the atmosphere through an exhaust system including a passageway formed in the housing, a part of which is an axial passage formed in a piston slidably mounted on the housing. In the normal-condition of the tool, compressed air is supplied to the lower surface of the cylinder to hold it in engagement with the main valve means, and the compressed air is also applied to the piston structure; forming apart of the exhaustvalve system to displace this valve to a condition in which the. interior of the upper end of the cylinderis connected to the atmosphere.

When the tool is to be operated, the lower surface of the cylinder and the piston means in the exhaust Valve assembly are connected to the atmosphere so that the cylinder moves downwardly away from the main valve to supply compressed air to the cylinderto drive the piston downwardly in a power stroke. 'The compressed air, when admitted to the cylinder, also acts on the piston structure in the exhaust valve to move this piston against a transversely extending valve surface to close off the exhaust .for the cylinder. When the control valve assembly is released to readmit compressed air to the lower surface of the cylinder and to the piston means in the exhaust valve assembly, the cylinder is shifted'upwardly to engage the main valve and the piston isshifted out of engagement with the valve surface in the exhaust valve assembly to place the upper end of the interior of the cylinder at atmospheric pressure. 1 To provide means for pneumatically returning the pis ton to its normal condition, the cylinder structure is providedwith a passageway connecting the lower end of the cylinder below the piston means with the fluid provided in the reservoir. Communication through this passageway is controlled by a pneumatically actuatedipiston return valve including a piston slidably mounted in a chamber' formed on the cylinder structure. This chamber is continuously supplied with compressed air from" the reservoir through a bleeder port, and this chamber is also placed in communication with the upper end of the interior of the cylinder through a passageway terminating in a port on the inner wall of the cylinder adjacentits upper end. When the cylinder is in its normal position, the compressed air supplied by the bleeder port acts on the pneumatically actuated control valve to close off communication betw een the reservoir and the lower end of the cylinder. Similarly, when the. cylinder is moved downwardly out of engagement with'the' main valve, the compressed air admitted to the upper end of the cylinder supplements the fluid pressure provided through the bleeder port to maintain the piston return control valve in a closed condition.

When the cylinder has been returned to a position engaging the main valve and the exhaust valve assembly has been opened to connect the interior of the cylinder to the atmosphere, the piston means remains adjacent the lower end of the cylinder in the position occupied at the end of the power stroke. However, the chamber in the control valve assembly is connected directly to the atmosphere through the exhaust valve assembly, and the compressed air in the fluid reservoir acts on the piston return control valve to shift this valve to its open condition. This opens the passageway in the cylinder so compressed air from the reservoir is supplied below the piston to pneumatically return it 'to a position adjacent .the upper end of the cylinder. At this time, one or a pair of resilient O rings carried on the piston seal the port or passageway'extencling to the chamber. in the piston re'turn..control valve so that the fluid supplied through the bleeder port builds up in the chamber and is effective to close the piston return control valve. This terminates the application of compressed air from the reservior to the portion of the cylinder disposed below the piston means. The light Patented June 22-, 1965 g the piston.

l 1 1G. 1 is a sectional view ofta pneumatically tion and which is shown in normal position;

FIG. 2 is an enlarged sectional view of'a piston return frictional engagement of the inner Walls or" by the sealing O-ringgener'ally' will: prevent the piston the a cylinder 1 the cylinder 18 is moved upwardly to engage the main valve assembly 30 so as to close oif communication befrom dropping from its normal position; However, if the V v pistondoes drop, the ch-ambe'r in the piston return control valve is again vented'to theatmosphere, and'this valve is momentarily opened to; supply air for returning" Many other objects and advantages of thepresent ii -1, I

vention will become apparent from consideringthe follow ing detailed description in conjunction with the drawings, in -which:

fastener driving tool which embodies the present'invencontrol valve carried on a'cylinderstructure included in the tool that illustrates the control valve in its normal condition; y a a a V FIG. 3 is a sectional view similar to FIG. 1 showing the if-astener driving tool in an operated condition at the termination of a power'stroke;

1 FlG.:4.is an exploded perspective view of the return control valve shown in FIG. 2;

FIG. 5; is a sectionalview similar to 1 and 3 illustrating the'tool in-its'condition after a power, stroke .1, and'prior to the return of the piston to its normal con 7 and 3,043,272. The; tool 19 includesa housing 12 comprising a r'earwardly extending hollow handle portion 12a.

and a generally vertical head or forward portion 12b. The cavity in the hollow handle portion 12a and a chamber 14 formed in the head portion 12bprovidea reservoir 15 I that iscontinuously supplied with a pressurized fluid, such as compressed air. A cylinder 18 movably'mounted in the chamber 14 slid-ably receives a piston 20' to the lower end of which is secured a driver blade 22L A nosepiece" structure 24 is-secured to the lower end ofrthe forward portion 12b of the'housing'ii and defines a drive track 26 to which suitable fasteners to be'driven, such as staples, are

supplied by a conventional magazine assembly (not Compressed air from the-reservoir '16 is' norshown). mally supplied by a manually actuated control valve assembly 28 to hold the open upper end of the cylinder 18 seated in engagement with a main valve assembly 30 se-' cured in a fixed position 'onjthe housing 12. The cornpressed air supplied by the "control valve assembly 28is also forwarded to' an exhaust valve assembly, indicated generally as 32, to hold this valve assembly in 'a position permit the compressed air to enter the cylinder 18 and drive the piston 20' and driver bladev22 downward-ly to engage and set a fastener supplied to the drive tr-ackr26.

'The control valve 28 also connects the exhaust valve assembly 32 to the atmosphere so'that it is operated to a closed position' by the compressed air admittedflto the' cylinder 18 thereby preventing theloss of 'fiuid pressure in the reservoir 16. The piston '20 remains in its position at the lower end of the cylinder 18 at the end of the power stroke until the control valve assembly 28is released to lfand to theeXha-ust valve assembly 32. At,this time,

actuated piston i Referring now more specifically tojthe construction of the housing 12, this housing 'canibe formed in any of the tween the interior of the cylinder 18 and the reservoir 16,

and the compressed air supplied to the exhaust valve asf sembly 32 operates this assembly to its open condition so that the fluid trappedin the upper end of the interior, of 1 the cylinder 18 above'the piston" 20 =is discharged .tothe atmosphere.

To control'the return of, the piston-20, apiston return control valve assembly 34 responsive to the pressure with! in the'upperend of the cylinder 18 is now operated, to'an,

open conditionto supply compressed-air from the resere voir 16 to the cylinder 118 below the piston 20. This ,com- 3 pressed air returns the piston- 20 to its normal position adjacent the upper'end of the cylinder 18. The'control valve 34' is automatically operated to afclosed'condition by the return of the piston 20 to prevent the supply" of 1 any additional compressed air from the reservoir 16 to the lower end of the cylindera'18f Therefore,'the pneumatically actuated fastener, driving tool 10 embodying the present invention includes; means for selectively supplying compressed air for returning the piston 20 to its nor mal condition only when communication between the reservoir 16 "and the interior of the cylinder 13 has been terminated and the cylinder has been connected to the atmosphere under the control of the improved exhaust valve assembly 32.

manners well known in the art'and comprises either an integral or multiple part structure. Infl-the illustrated constructiomthe top of the head portion 12b and the upper endof'the chamber 14 is provided with anopening' A closed by a removable cover 35 on which the main valve' assembly '30 and the exhaust valve assembly 32- are. mounted. The chamber 14 is, provided with a larger,

diameter, portion 14a anda smaller diameter portion 14b ,for slidably receiving thecylinderlS. An upperlportion of the cylinder 18 is provided withan upper of first piston portion slidably mounted in'the' larger diameter portion 14a and sealed by. an O-ring 36,. A second' or smaller diameter-portion at the lowerend of thecylihderls is slidably mounted in the smaller diameter portion 14b of 1 the chamber and'is sealed by an Q-ring'38.

To provide means for selectively connecting the lowerend of the'interior ofjthe cylinder 18 to the atmosphere, I

a lower cylinder exhaust valve' assembly 39 is provided.

The assembly 39 includesvagenerally cylindrical valve-- member 4tTslidably mounted in an enlargedportion-Hoof the smaller diameter portion 14b ofthe chamber 14. 'A" compression spring 41 normally urges the element 1 a upwardly to seat'a resilient,- circular valve-element 42 carried on the upper end of the member 40 on aninclined valvesurf ace143 on the housing to close communication between the .lowerend of the interior of the: dylindeirlS l r and :aplurality of exhaust ports 44, in the head portion 1250f the housing12; A resilient O-ring 45 carried on v the valve member 40 seals the interface between the i wall'of theenlarged portion 140 and the outer surface spring 41 to close thelower end of the cylinder '18, and

the lower end of the cylinder, which is provided witha plurality of notches or rece'sseslSiz, is spaced slightly above the upper end oftheavalve member 40.; When the cylinder '18 is moved downwardly to open its top, rts lower end engages the valve member 40 and moves it.

' downwardly againsttheaction of the spring ,41tomove1 .again supply compressed air to a portion of the chamber 1 the resilient valve element 42 out of engagement with the seat 43; Thisplaces' the lower interior of the cylinder 18 in communication with; the atmosphere; through the V recesses 18a and the ports 44 at least as soon as the top of the cylinder 18 is opened to the compressed air in the reservoir 16. When the cylinder 18 is restored to its normal position at theend of a cycle otopera-tion, the spring 41 biases the valve element 42 into engagement with the seat 43 to close the lower interior of the cylinder 18; Since the valve assembly 39-includes the resilient elements 42 and 45 for sealing the lower interior of the cylinder 18, the loss of air sometimes encountered in prior tools sealed by m'etal-to-metal interfaces is avoided. Further, the element 42 provides a tight seal without requiring the elongated metal-to-metal seal previously used and permits the connection to the atmosphere to be opened with less downward movementv of the cylinder 18 with the result that the lower end of this cylinder is connected to the atmosphere at least as soon as compressed air is ad- 'mitted to the top of the cylinder 18. In some prior tools, the exhaust for the lower end of the tool was not opened until after the top had been opened with a resultant decrease in the power available for driving the blade 22.

The piston 28 includes an upper flanged portion a having a recess in which are disposed two resilient O-rings 46. A lower depending portion of thepiston 20 is secured to the upper end of thedriver blade 22 by a pin 48. The downward movement ofthe piston 20 is arrested by a resilient bufier assembly comprising an annular body 50 of resilient material encircled by a metal sleeve 52 biased against the bottom wall of the chamber 40 by the spring 41. The body 50 includes an axial opening through which the driver blade 22 extends.

The main valve assembly which is secured in a fixed position on the closure cap comprises a circular sheet 54 of resilient material having an outer diameter approximately equal to theouter diameter of the upper portion of the cylinder 18. The center of the. sheet 54 is provided with an opening for receiving a depending cy lindrical portion 35a on the closure cap 35 which also extends through a central opening in a rigid retaining plate 56 having an outer diameter slightly less than the inner diameter of the upper portion of the cylinder 18. The resilient valve element 54 and the plate 56 are secured to the closure 35 by one or more machine screws 58.

The exhaust valve assembly 32 which is controlled by the control valve assembly 28 includes a piston 60 slidably mounted in a chamber or cylinder 62 in the closure cap 35 which communicates with an exhaust passage 64 that passes through the depending portion 35:: on the closure cap 35 to the interior of the cylinder 18. The

lower end of the piston 60 is slidably mounted in a reduced diameter portion of the chamber 62, and the upper end of the piston 60 is slidably mounted within a centrally disposed opening in an annular guide member 66 that is disposed within the upper end of thechamber 62'. V A resilient sleeve 68 is mounted in an enlarged upper end of an exhaust passage 70 passing through the piston 60 and includes an upper end portion projecting above the upper 28 controls the selective operation of the exhaust valve assembly 32 and the movement of the cylinder 18 into and out of engagement with the main valve assembly 30. The valve assembly 28, which can be of the type disclosedand described in detail in the above-identified patents, includes 86 to the pant of the larger diameter portion 14a of the chamber 14 that is disposed between the sealing O-rings 36 and 38. Since the lower effective area on the cylin der 18 is greater than the upper effective areaon the cylinder 18 exposed to the pressurized fluid in the reservoir 16, an upwardly directed component of force is applied to the cylinder 18 to normally force its upper edge into engagement with the resilient valve element54. This normally closes ofi communication between the upper end of the interior of the cylinder 18 and the pressurized fluid in the reservoir 16. The compressed air-supplied to a the lower end of the greater diameter portion'14a of the surface of the piston adaptedto be moved into and 8 out of engagement with a transverse wall element or valve seat 72 secured to the closure cap 35. 7 v

In the normal condition of the tool 10, the exhaust valve 32 is in an open condition connecting the upper interior of the cylinder 18 with the atmosphere through the passageways 64 and 70 and a plurality of transverse passageways 74 formed by the plate 72 and the closure cap 35. The exhaust valve assembly 32 is normally held in this open condition by compressed air supplied to the chamber 62 through a passageway 76 in the forward portion 12b of the housing and a passageway 78 in the closure cap 35. This compressed air acts on the upper effective area of the piston 60 disposed wthin the chamber. 62 to force the piston downwardly against a stop chamber 14 is also sup-plied through the passageways 76 and 7 8 to act on the upper area of the piston 68 disposed within the chamber 62 to hold the exhaust valve assembly 32' in its normal condition in which the'upper end of the interior of the cylinder 18 is' vented to the atmosphere through the passageways 64, 7 8, and 74.

When the control valve assembly 28 is actuated by pivot ing the trigger element 82 in a counter-clockwise direction about the pivot pin 84, the valve assembly 28 closes off communication between the passageway 86 and the pressurized fluid in the reservoir 16 and connects the passageway 86 to the atmosphere so that the compressed air in the chamber 62 and the portion of the chamber 14 disposed between the O-rings 36 and 38 is exhausted to the atmosphere. The compressed air acting on theluppe-r effective surfiaces of the cylinder 18 exposed to the pressurized fluid within the reservoir 16 now produces a downwardly directed component of force that shifts the cylinder 18 downwardly from the normal position illustrated in FIG. 1 to the displaced position illustrated in FIG. 3. In moving downwardly, the cylinder 18 moves the valve member 40 downwardly to move the valve element 42 out of engagement with the seat 43 to connect the lower interior of the cylinder 18 to the atmosphere. 7 V

This permits the air trapped below the piston 20 to be dlscharged to the atmosphere during the power stroke of the fastener driving means; As the upper end of the cylinder 18 moves out of engagement with the resilient valve element 54, the pressurized fluid or compressed air in the reservoir 16 flows into the open upper end of th cylinder 18 and drivesthe piston 28 and the connected driver blade 22 downwardly to engage and drive a fastener or staple supplied to the drive track 26. At the lower end of the power stroke illustrated in FIG. 3 of the drawings, the lower end of the reduced diameter portion of the piston 20 engages the upper edge of the resillent bumper or buffer element 50 to resiliently cushion the term nation of the power stroke.

When the upper'end of the cylinder 18 moves out of engagement with the resilient valve element 54 in the main valve assembly 38, compressed air is admitted tothe lower end of the passageway 64. Sinc'e'the compressed air in the chamber 62 acting on the upper efl ective surface of the piston 60 has'been'discharged to the atmosphere by the actuation of the cont-r01 valve assembly 28, and since the area of the passageways 64 and 70 is small relative'to the volume of compressed air now supplied to the cylinder 18, this compressed air is effective through the passageway 64 to act on the reduced diameter lower effective surface of the piston 69 to move this piston upwardly to the position illustrated in FIG. 3 in which the upper end of the resilient sleeve 68 is held in sealing engagement with the transversely extending valve seat 72.

a are? This closes communication between the passageway '70 and the passageways 74 to close the exhaust valve assem-j bly 32 and prevent the loss of compressed air from the reservoir 16. The fastener driving toollii remains in the condition shown in FIG. 3 of the drawings with the ex:

haust valve assembly 32 in a closed condition and with the, j cylinder 18 and the piston 2%) moved downwardly to their displaced positions until the controlvalve assembly 28 isreleased. I V a j a At: this time, the passageway 86 is closed'ofif from coni- 7 1 and 2 in which'the valve portion 96aseats-againstthe resilient valve element 102 to prevent communication 1342-. tween the port 94 and the passageway 83. The com-4 munication with the atmosphere and is'againtconriected to the pressurized fluid in "the reservoir 16. This fluid flows into the portion 14a of the chamber 14 bonded by the O-rings 36 and 38 and, because of the greater effective lower surface on the cylinder 13, moves this cylinder up- Wardly so that'its upper edge again engages the resilient valve element 54 in the main valve assembly 31 to close E communication between the reservoir 16 and the interior of the cylinder 18 (FIG. '5). When the cylinder 18 moves upwardly, the valve member h) is moved upwardly by the spring 41 to seat the valve element 421011 the surface .43 to close off oornmunication'between theatmosphere and the lower endofthe interior of the cylinder 18. The compressed air supplied to the chamber portion 14a also flows through the passageways 76 and 78 into the chamber 62. This compressed air actson the greater upper effective area of the piston 60 to move this piston downwardly from the position shown in FIG. 3

to the position shown'in FIG. 5. Whenthe jpiston 6e moves to this position, the upper end of theresilient sleeve 7 68 moves out of engagement withthe element 72 so that the upper end of the interior of the cylinder 18 is again placed in communication with the atmosphere through main valve assembly 363, are "disposed on opposite sides of the port terminating the passageway 1-10. z-Th'e bleeder passageway 168 I continuously supplies pressurizcd.. fluid from the reservoir 16 tothe chamberQtl which acts on V .theupper surface of the 'pistonipor-tion 96b to force the member 96 downwardly to the position shown'in FIGS,

pressed air acting .on the upperlsur-face of the piston por tion 961') holds the valve assembly 34 in a closed condu tion even though the compressed air from the reservoir, 16 acts on the lower surfaces of this piston portionber t cause the upper surfaces of the piston portionhaveea greater eilective area; thanthe lower surfaces. 7

When the control valve a ss-emblyIZS is actuated to operate the tool It) to the position illusttra-ted in 'FlG.,3 o

the drawings, the cylinder '18; is moved downwardly out 7 of engagement with'the main valve assembly 39, and the piston is driven-'tl 1rough a power stroke When the piston 2t) moves downwardly, the O-rings 46 move away from the port'termin a-ting the passage 11050 that the chamber 90 is also supplied with pressurized fluid from I the uppe'iiend of the cylinder ls through the passageway the passageways 64-, 7t), and 74m exhaust the pressurized fluid trapped in the upper end of the cylinder '18 when this cylinder was moved into engagement with the main valve assembly 3i). The reduction in the pressure in the'upper endof the cylinder 13 automatically controls the operation of the piston return valve assembly 34 to, supply compressed air to the lower end of the interior of the'cyl in' der 18 to return the piston 2% to its normalposition.

The pistonreturnvalve assembly 34 is mounted on the cylinder '18 and, morels pec-ific'ally, is mounted on a projecting portion 18 (FIGS. 2, 4 and 6) adjacent the upper end of the cylinder 18 to control communication between the reservoir l and thelowe'r end of the in-' terior of the cylinder 18 through a passageway S-Sformed in the wall of the'cylinder 118. The piston'returnvalve assembly 34 includes a pair of aligned and-cylindrical chambers 90 and 92 for-med'in the projecting portionlfia;

' Theloweriend of the chamber 9,2 is placed in communicationwith the reservoir 16 through a port or passageway 94. A member 95 includes a conical or tapered valve portion 96a disposed in the chamber-92 and a piston pOrtion 96a slidably mounted in the chambers 9i and 92; 'A

pairiof'O-rings 98 and 1% seal the interfaces between the member 96 and the chambers 90 and 92 in two spaced positions.

resilient O-ring or. valve element, 1432 to selectively control communication between the poi-1:94 and the passage way 88. The upper end of'the chamber 99 isclosed by a plug 104 which is received within the upper end of the chamber 90 and carries a sealing 0-ring1t36. A bleeder passage 108 in the plug 194 continuouslysupplies presa surized fluid from the reservoir, 16 to the chamber 1% in the area disposedbetween the lower or inner end of the 7 piston 20 is disposed in its normal position adjacent the The lower end of thevalve portion 96a is adapted .to be moved into and out of engagement :with av passage 11!)- so that thejconnection between the atmos 119. This provides an additional source of pressurized fluid. for maintaining the valve portion 96:: of the mem.--

ber 96 in engagement with the valve element 102. When the control valve: 28 is released andrthe cylinder 18 moves upwardly into engagementwith the mainvalve assembly 39, the exhaust valve assembly 32 is also ac tuated to its normal or open position shown in FIGS. 1 v and 5 so that the interior of the cylinder 18 disposed above 7 thepistonZt) is connected to thefatmosphere- Since the passage 11%? is in communication with the interior of the upper end oithe cylinder 18, the pressurized fluidsup pliedthrough the bleedertpassage .163 is exhausted tothe atmosphere, and the portion of the chamber 99 disposed betweentheipiston portion 96b and the plug 194 isplaced substantially 18.1 atmosphericpres-s'ure. 'In, one tool 10 constructed in accordance ,Withthe present invention, the

diameter of the larger passageway'llti is twice'that ofv p the smaller passageway 108. The compressed air supplied through the port 94 acts on the lower effective 'sur-faceof .the piston port-ion 96b below the sealingO-ring 100 to i provide an upwardly directed force that moves the mem:

.ber 96 until'the upper surface of the pistonportion 96b engagesabossed portion 134:: on the plug 194. -.-Tl1is 7 moves the .valve portion 9hr: out of engagement with the sealing O-ring 102, and the compressed air continuously supplied tothe passage .or port 94 from the reservoir 16 flows. through the passageway SSto the interior of the cylinder 18 below the piston-20 as'illustrated in F IGSJS and 6 of the drawings.

Since the interconnection'between the atmosphereand lower end of the interior of the cylinder'18 has previous,-

1y been closed by moving the cylinder 18 upwardly touthe position illustrated in FIG. 5,:the compressed air supplied by the passageway-Essen on the lower surface of the piston 2i to move the piston upwardly to the, position shown in; FIG. .1 of the drawings. When the piston 20 is restored toits normal position, the O-rings 46am. again disposed-on opposite sidescf the port terminatingthe phere and thechamber provided by the open exhaust valve assembly3-2 is terminated. Thus, the preswsurized fluid supplied tthrough' the ble'eder passage 108 from the reservoir 16 accumulates within the-chamber 90.

Since the upper efiectiye area. of the piston porn'on 96b of the member 96 is greater thantthe lower effective sue 'facethereot, the compressed air in the "chamber 90 pro. vides a downwardly directed force thatshifits the member 96tuntil the valveportion 96a again engages the valve 7 element 102 to'close communication between the port'94 and the passageway '88. Thus, the supply of pressurized fluid to the lower end of the cylinder 18 is terminated as soon as the piston 23 is restored to its normal condition. The piston return valve assembly 34 is now restored to the normal condition'illustnated in FIGS. 1-3 of th drawings. In the event that the compressed air trapped in the lower end of the cylinder 18 becomes dissipated by leakage prior to theinitiation of the next, cycle of operation of the tool 10, the piston 20 usually will not drop below its normal position because the light frictional eugagement of the inner wall of the cylinder 18 by the rings 46 retains the piston 29 in its retracted or normal position. In the event that the piston 20 does drop, the O-rings 46 again open the passageway 11%) so that the chamber 90 is vented to the atmosphere through the open exhaust valve assembly 3 2 This operates the Valve assembly 34 to supply compressed air below the piston 29 for returning it to its normal position. The piston 20 causes the reclosure of the valve assembly '34 as soon as the piston is returned to its normal. position.

Although the present invention has been describedwith reference to a single illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments can .be devised by those skilled in the art that will fall within the spiritand scope of this invention.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. A fastener driving apparatus comprising a housing supplied with a pressurized fluid and including a cylinder, fastener driving means including piston means slidably mounted in the cylinder, control means for alternately connecting the upper end of the cylinder means to the atmosphere and to the fluid to drive the piston means, and means responsive to the pressure inthe uppercnd of the cylinder and controlled by the connection of the upper end of the cylinder to the atmosphere for selectively supplying fluid to the cylinder below the top of the piston means when the upper end of the cylinder disposed above the piston means is placed at atmospheric pressure.

2. A fastener driving apparatus comprising a housing supplied with a pressurized fluid and including a cylinder, fastener driving means including piston meansfslidably' mounted in the cylinder, control means for alternately connecting the upper end of the cylinder means to the atmosphere and to the fluid to. drive the pistonjmeans, valve means for supplying fluid to the cylinder means below the piston means, and pressure responsive means communicating with the upper end of the cylinder for selectively operating the valve means tosupply pressurized fluid below the piston means when thepressure within the'upper end of the cylinder means approaches atmospheric pressure. 1 l

3. A fastener driving apparatus comprising a housing including a reservoir continuously supplied with ap'res surized fluid and cylinder means havingan open end exposed to the fluid, fastener driving means including piston means slidably mounted in the cylinder means, main valve means normally closing the open end of thecylinder means, means for producing a separation between the main valve means and the end of the cylinder means to admit fluid to the cylinder for driving the piston means, exhaust means fordischarging pressurizedfluid from the cylinder means above the piston means, and piston return means controlled by the pressure within the cylinder means above the piston means for selectively supplying fluid to the cylinder means below the top of the piston means to return the piston means to a position adjacent the open end of the cylinder means when the exhaust means discharges the pressurized fluid from the cylinder means above the piston means.

4. A fastener driving apparatus comprising a housing including a reservoir continuously supplied with a pressurized fluid and cylinder means having an open end exposed to the fluid, fastener driving means including piston means, means for producing a separation between the main valve means and the end of the cylinder means to admit fluid to the cylinder for driving the piston means, and a pressure responsive valve means for controlling the flow of pressurized fluid between the reservoir and a point in the cylinder disposed below the top of the piston means; said pressure responsive valve means beingcontrolled by the pressure in the cylinder means above the piston means and communicating with the cylinder means adjacentthe open end for selectively supplying fluidfrom'the reservoir to the cylinder means below the top of the piston means when the pressure in the cylinder meansabove the piston means approaches atmospheric pressure. p j

5. A fastener driving apparatus comprising a housing including areservoir continuously supplied with a pres surized fluid and cylinder means having an open end exposed to the fluid,1fasten-er driving means including piston meansslidably mountedin the cylinder means, main valve means normally closing the open end of the cylindermeans, means for producing a separation between the main valve means and the end of the cylinder means to admit fluidto the cylinder for driving the piston means, ex: haust means for connecting the portion ofthe cylinder means above the piston means to the atmosphere when the open end of the cylinder means is closed by the main valve means, return means for supplying fluid toithe.

cylinder means below the top of the piston means to return the piston means to a position adjacentthe end of the cylinder means, and means controlled by the pressure within the cylinder above the piston means and responsive to the connection of the cylinder means above the piston means to the atmosphere by the exhaust means for ,selectively operating the return means to supply fluid to the cylinder means below the piston means.

6. A fastener driving apparatus comprising a housing admit fluid to the cylinder for driving the piston means,

exhaust means for connecting the portion of the cylinder means above the, piston means to the atmospherewhen the open end'of the cylinder means is closed by the main valve means, control valve means for supplying fluid from the reservoir to the cylinder means below the top of the piston means, and pressure responsive means for operating the control valve means and communicating with the cylinder means, above the piston means.

7. A. fastener driving apparatus .comprising a housing supplied with a pressurized fluid and includinga cylinder, fastener driving means including piston means slidably mounted in the cylinder, control means for alternately connecting the upper end of the cylinder means to the atmosphere and to the fluid to drive the piston means, valve means for supplying fluid to the cylinder means below the. piston means, control piston means for moving the valve means between opened and closed positions, means for applying fluid to the control piston means, and meansincluding a passage communicating with the upper end of" the cylinder means for connecting the control pisexposed to the fluid, fastener driving means including pis-.

ton means slidably mounted in the cylinder means, main valve means normally closing the open end of the cylinder means, means for moving the main valve means and cylinder means into and out of engagement to selectively admit r the fluid to the end of the cylinder means, exhaust means for connecting the portion of the cylinder means above the -r neans. a a i 9. A driving device comprising a housing including a- I reservoir of pressurized fluid, a cylinder movably mounted piston tothe atmosphere.

piston means to the atmosphere when theimain valve,-

means closes the end of the cylinder means, and control means responsiveto closing the 'cylinderuendfand connecting the closed cylinder'to the atmosphere wfor supplying" fluid to the cylindermeans'below the top of piston on the housing and-havingan end exposed to the fluid in the reservoir, driving means including a piston slidably for moving the cylinder into and out of, engagement with the main valve means to open and close the cylinder, and control valve means carried on thercylinder and selectively operableto supply fluid to the cylinder, below the piston;

tween positions in which the opening is opened and closed, 1

v and means for connecting the cylindrical portion to the 0, mounted in the cylinder, main valve means, control means fluid and the atmosphere ,to' move the piston meansto selectively'open andclose the exhaust means,

14. A fastener driving apparatus comprising a housing including a reservoir continuously supplied with a'pressurized fluid and a cylinderhaving an end exposed to the fluid; fastener driving means including piston 'means slidably mounted in the cylinder; main valve means normally closing the open end of the cylinder; control means for separating the cylinder and main valve means to admit fluid. for driving the piston means; fluid conveying. means 10. The drivingzdevice set forth in .clairn 9 including means responsive to movement of the cylinder-for selec- 1 tively connecting the portion of the cylinder below the I a 11. A driving dev ce comprising a housing including a reservoir of pressurized fluid, a cylinder movably mount-i ed on the housing and having an end exposed to the fluid a movablevalve member-r'novableinto and out of abutting in the reservoir, driving means including a piston slidably mounted in the cylinder, main valve means, control means for moving the cylinder into and out of engagement with the main valve means to open'and close the cylinder, fluid conveying means on the cylinder connecting a portion of the cylinder below the end to the reservoir, control valve means carried on the cylinder for controlling the'flowof fluid through the fluid conveying means, and means for selectively operating the control valvemeans. t 12. A fastener driving apparatus comprising a including a cylinder,-fastenerdriving means including a piston slidably mounted inthe ,cylinder, control means for selectively, supplying a pressurized fluid to the cylinder to drive the pistonthrough a single powerstroke from a I normal position to a'displaced position, said control means also:inc luding rneansrfor connecting the cylinder to the atmosphere to permit the piston to be returned from the displaced'position to the normal position, piston return= meansrincluding acontrol valve for'supplying fluid to the cylinder to return the piston to its normal position, and

1 fluid responsive means for controlling the operation ,of

the control valve and including a port inthe wall of the cylinder adjacent the normal position of the piston, the port being located in'the wall ofthe cylinder toi beclosed bythe piston when the piston is disposed in the normal position to close the control valve, the port being uncovered when the piston is moved to'the displaced position to connect the fluid responsive means to the atmos der-to return the piston to the normal position.

13.. A fastener driving apparatus comprising a housing including a reservoir supplied with a pressurized fluid,

on the housing extending between theatm'osphereand the cylinder at a pointbelow'the piston means; and an exhaust-valvearrangement for selectively opening and clo'singthe fluid conveying means; said exhaust l valve ar rangement including a valve seat carried on the housing,

engagement with the valve seat to open and close the exhaustvalve arrangement, andresilientsealing meansinterposed-between the valve seat and'the valve member. A

15." The fastener driving apparatus set forth in claim 14 1 in which said cylinder, ismovably mounted in the housing and in which the valve member includes means engaged by the cylinder to move the ,valve member to a position opening the exhaust valve arrangement. a

16. A;fastener driving apparatus comprising a housing having both a cylinder and a reservoir suppliedwith a housing phere to open the control valve to supply fluid to the cyling,

main valve means secured to the housing in a fixed posi tion therein, a cylinder slidably mounted on the housing and having an open end exposed to the fluid in the reservoir, fastener driving means including a piston slidably mounted in 'thecylinder, control means for moving the cylinder into and out of engagement with the main valve a means to selectively admit fluid to. the cylinder, exhaust meanstincluding an opening communicating with the i cylinder below the main valve means, said'opening including a cylindrical portion, piston means slidably mounted in the cylindrical portion of the opening and movable bei admit fluid to the cylinder pressurized fluid, fastener driving means including drive.

piston means slidably mounted' in rthe cylinder, control means for alternately connecting the upper end of the,

cylinder means to the atmosphere and to the fluid in the reservoir todrive the piston means, valve means 'for sup plying fluid to the cylinder meansibelow the'drive piston phere'to control the operationof the valve means, v

17. The apparatus set; forth in claim 16yin which the passage includes a port selectively opened and closed, by the drive piston means; l

' 18. The fastener driving apparatus set forth 'in claim 12 in whichthe fluid responsive means'includes' aslidably mounted 1 control pistonnormally biased to a-positio'n' closing the control valve by the fluid and in which the 1 connection of the port, tojthe' atmosphere exhausts the fluid acting on the control piston 'through'the port';to

permit the control piston to open the control valve-and for returning the piston to the 1 normal position.

ReferencestCited hythe Examiner UNITED STATES @PATENTS 1,494,030 5/24: Slater p 91--399' 2,944,5227 73/60 Doyle 91 -423, 2,985,139 5/61 Powers et al. 91-.-416 3,040,709; 6/62. Wandel 91-416 3,094,900 6/63 FRED E. ,E NGE LTHALE R,LPrimary Exa iner; SAMUEL LEVINE, Examiner.

Wandel et in. 91-423," 

1. A FASTENER DRIVING APPARATUS COMPRISING A HOUSING SUPPLIED WITH A PRESSURIZED FLUID AND INCLUDING A CYLINDER, FASTENER DRIVING MEANS INCLUDING PISTON MEANS SLIDABLY MOUNTED IN THE CLYINDER, CONTROL MEANS FOR ALTERNATELY CONNECTING THE UPPER END OF THE CYLINDER MEANS TO THE ATMOSPHERE AND TO THE FLUID TO DRIVE THE PISTON MEANS, AND MEANS RESPONSIVE TO THE PRESSURE IN THE UPPER END OF THE CYLINDER AND CONTROLLED TO THE ATMOSPHER FOR SELECTIVELY SUPEND OF THE CYLINDER TO THE ATMOSPHERE FOR SELECTIVELY SUPPLYING FLUID TO THE CYLINDER BELOW THE TOP OF THE PISTON MEANS WHEN THE UPPER END OF THE CYLINDER DISPOSED ABOVE THE PISTON MEANS IS PLACED AT ATMOSPHERIC PRESSURE. 